This invention relates to a new and improved stabilized and reinforced fabric and its process for manufacture, and to the laminates produced therefrom.
Reinforced fabrics which are employed in resin matrices are frequently formed into stacks or other shapes that require the fabric to be stabilized in a particular position or configuration. Various techniques are known to stabilize the fabric structure for this purpose, and typical publications in the area of fabrics and reinforced fabrics include U.S. Pat. Nos.: 3,844,822; 3,914,494; 4,092,453; 4,237,175; 4,370,784; 4,407,885; 4,410,577; 4,518,640; 4,539,249; 4,590,122; 4,606,968; 4,680,213; 4,714,642; 4,748,996; 4,799,985; 4,818,318; 4,871,491; 4,874,563; 4,902,537.
However, the prior art does not provide a reinforcing structure that can be easily contoured, stacked or positioned, while still retaining its stability as a fabric, when employed as a reinforcement. For example, U.S. Pat. No. 3,914,494 describes a carbon tape reinforced with a small number of weft picks. However, these weft picks only provide reinforcement for a tape width of up to approximately three inches, and this limits its use considerably.
Other fabric structures containing reinforcing thermoplastic binder fibers which stabilize the fabric structure when heated in a stacked assembly, are disclosed in U.S. Pat. Nos. 4,407,885 and 4,680,213. However, the relatively large amounts of thermoplastic fiber employed in the fabric tend to render the fabric structure stiff after a preliminary application of heat to stabilize the fabric.
Many types of fabrics are used to reinforce composites, and it would be desirable to provide a fabric with a reinforcing fiber having a composition which is compatible with the composite matrix. However, in the case of an epoxy matrix, use of an epoxy fiber reinforcement is not usually employed commercially since epoxy resins are not generally formable into fibers. Also, while many polymers can be formed into fibers, the process is expensive, and adds to the cost of a reinforced fabric. Consequently, it is desired to provide a fabric for use in composites, the fabric being sufficiently stabilized so that it is easily manipulated and also conformable to a substrate for subsequent molding, without being too stiff.